Catalytic hydrocarbon conversion processes



Patented Jan, 316, 1945 CATALYTIC HYDROCARBON CONVERSION PROCESSESMeredith M. StewarhBeacon, N. Y., assignor to The Texas Company, NewYork, N. Y., a corporation of Delaware Application llecember 31, 1942,Serial No. 470,710

8 Claims.

My invention relates to catalytic hydrocarbon conversion processes, andparticularly to an improved method for reactivating spent catalysts insuch processes.

In high temperature catalytic hydrocarbon conversion processes, such ascracking and repensive, and has been disadvantageous for the Ireactivation of powdered catalysts in view of the difllculty ofeparating a fine powder from hot combustion gases.

An object or my present invention is to provide an improved method forreactivating hydrocarbon conversion catalysts.

Another object or my invention is to provide a liquid phase process forthe removal of carbonaceous deposits irom hydrocarbon conversioncatalysts.

A further object of my invention is to provide a process for the removalof carbonaceous deposits Irom hydrocarbon conversion catalysts byhydrogenation in the presence of a liquid phase hydrogen carrier.

An additional object of my invention is to provide an improved cycliccatalytic process for hydrocarbon conversion in which the catalyticreaction is eflected in the presence of a liquid hydrocarbon phase, andthe carbonaceous deposits are removed from the partially spent catalystby hydrogenation in the presence of a liquid phase hydrogen carrier.

Other objects and advantages of my invention will be apparent from thefollowing description:

In accordance with my present invention, carbonaceous deposits areremoved from hydrocarbon conversion catalysts by hydrogenation in thepresence of a liquid phase hydrogen carrier. Any material which iseasily dehydrogenated at the temperature and pressure employed for thereactivation will serve as a hydrogen carrier in this process. Thematerial employed should, of course, have no adverse effect on thecatalyst itself, even ous catalyst deposits. The hydrogen carrier isever, I prefer to employ as hydrogen carriers compounds which, as suchoras their dehydrogenation products, are not undesirable in the catalytichydrocarbon conversion reaction mix: ture, and hence do not have to becompletely separated from the recycled catalyst. For this purpose,hydrocarbons which are easily dehydrogenated at the reactivationtemperature and pressure are the most advantageous hydrogen carriers.

I prefer to employ as hydrogen carriers in my process cyclichydrocarbons which are at least partially saturated, i. e., lessunsaturated than aromatics. cyclic or polycyclic, and may be eitherpartially or completely hydrogenated. 'I'he cyclo-parafilns andcyclo-oleflns having five or six carbon atom rings are examples of thisclass of compounds. I generally prefer to employ hydrocarbons having sixcarbon atom rings, 1. e., the hydro-aromatics, and particularly thepolycyclic hydroaromatics. It should be understood, in this connection,that the term polycyclic" is used herein and in the appended claims todesignate bicycllc compounds as well as those having more than tworings.

' ogous polycyclic compounds, with or without alkyl side chains, areexamples of my preferred class of hydrogen carriers. Mixtures of suchcompounds, or hydrocarbon fractions containing ubstantial amounts ofsuch compounds may be used. Naphthenic petroleum fractions havingboiling range of the order of 300-600 F. are inexpensive materials welladapted for use as hydrogen carriers in my process.

If the hydrogenation is effected by means of gaseous hydrogen, thehydro-aromatic hydrocarbon will serve primarily as a hydrogen carrier,and will be continuously dehydrogenated and rehydrogenated. In suchcases, at the conclusion oi. the reaction, little if any aromatichydrocarbons will be present in the reaction mixture.

However, any hydrogen carrier may also serve as a hydrogen donor in thereaction, and may constitute the only source of hydrogen for reactionwith the carbonaceous catalyst deposits. The use of hydro-aromatichydrocarbons in this manner is very advantageous, since substantialquantitles of valuable aromatic hydrocarbons may thus be producedsimultaneously with reactivation of q the catalyst.

suitably a compound which may readily be separated from the catalyst,and whose dehydrogenation products may also be separated easily. How-The amount of the cyclic hydrocarbon to be employed as a hydrogencarrier may vary over a considerable range. Inany case, there should besuflicient to completely wet the surface of the Such hydrocarbons may bemono- Tetralin and decalin, and anal-- catalyst; and if the hydrocarbonis to serve as the sole source of hydrogen for the reaction, it shouldbe present in a concentration such that the amount of hydrogen liberatedby its dehydrogenation is at least equivalent to the carbon content ofthe deposit on the catalyst. Generally, however, the amount of thecyclic hydrocarbon should be much in excess of either of the aboveminimum requirements. It is preferable to employ sufficient hydrocarbonto obtain a catalyst slurry which may be easily handled and agitatedduring the hydrogenation reaction. A very large excess of the hydrogencarrier or hydrogen donor may be used, if desired. However, whenemploying hydro-aromatics as hydrogen donors it IS preferable to avoid alarge excess, in order that the aromatics produced may be recovered at arelatively high concentration.

The hydrogenation reaction is effected at a temperature in excess of 700F., and preferably at a temperature of about 750 F. Higher temperaturesmay be employed if desired, but should not be sufllciently high to causeundue cracking of the hydrogen carrier employed.

The pressure at which the hydrogenation reaction is effected should besuflicient to maintain the hydrogen carrier in liquid phase at thereaction temperature. The minimum pressure will thus vary for diiierenthydrogen carriers, but

' for hydro-aromatic hydrocarbons having boiling 3 points at least ashigh as that of tetralin, a pressure of 400pounds per square inch willusually be suiiicient. Much higher pressures, e. g. initial pressures of1000-3000 lbs. per square inch are usually desirable. If gaseoushydrogen is employed in the reaction, the pressure may be controlled bythe introduction of the hydrogen. when hydrogen is not used, pressureshigher than the vapor pressure of the hydroaromatic hydrocarbon or otherhydrogen carrier may be obtained by the introduction of an inert gas,such as nitrogen, natural gas, or the like.

The contact time employed in the hydrogenation reaction will depend onthe temperature used, and the degree of reactivation required. At atemperature of 750 F., contact times of 1-6 hours should generallyprovide suflicient reactivation of partially spent catalysts. Shortercontact times may be employed if there is thorough agitation of thereaction mixture than is required for a relatively static mixture, and Iprefer to provide suitable agitation in all cases.

At the conclusion of the reaction, the reactivated catalyst may beseparated from the hydrocarbons by filtration or other suitable means,and may, if desired, be washed or otherwise further treated beforerecycling. However, it is generally suflicient merely to recover thereactivated catalyst in the form of a concentrated slurry. This may beaccomplished by gravity settling and decanting, or by flash vaporizingthe bulk of the hydrocarbons from the hot reaction mixture at reducedpressure.

My reactivation process is applicable to the treatment of anyhydrocarbon conversion catalysts which have become deactivated due tocarbonaceous deposits. Such catalysts are insoluble in hydrocarbons, andare usually entirely inorganic in composition. They are used in fixedbed operations and in fluid catalyst" operations for relatively hightemperature reactions such as cracking, reforming, hydroiorming, and thelike. My reactivation process is especially applicable to alumina-silicacatalysts, such as the clay types of cracking catalysts. Themontmorillonite gears-2'4 clays, and especially the highly active formsof these clays, such as Superflltrol," are examples of cracking catalystwhich may advantageously be reactivated by my process.

5 A further phase of my present invention comprises controlling thereaction conditions of the catalytic hydrocarbon conversion reaction sothat the catalyst deposits obtained are of a nature particularly adaptedto my reactivation treatment. This is effected by carrying out thehydrocarbon conversion reaction in the presence of a liquid hydrocarbonphase, so that the car bonaceous deposits formed on the catalyst will beof a more tarry and less coke-like nature. The entire reaction mixtureneed not be maintained in the liquid phase, but there should besufll'cient liquid hydrocarbon to maintain the catalyst surfacecompletely wet during the reaction. This typ of operation is bestadapted to the catalytic treatment oi high boiling petroleum fractions,such as gas oils, reduced crudes, and the like. For the catalytictreatment of lighter fractions, such as naphthas, highly activecatalysts are required to efl'ect reactions at the relatively lowtemperature required to maintain a liquid phase. Such light fractionsmay, however, be treated at higher temperatures in the presence of ahigher boiling fraction to provide a liquid phase.

0 When the catalytic hydrocarbon conversion is effected in the presenceof a liquid hydrocarbon phase, the partially spent catalyst mayadvantageously be extracted with a solvent to remove a portion of thetarry deposit. Any organic liquid which is known to have solvent.properties for tarry or resinous petroleum derivatives may be used forthis purpose. Petroleum hydrocarbons are suitable for this purpose, andit is generally advantageous to employ the same hydro- 40 aromatichydrocarbon or petroleum fraction containing hydro-aromatics, which isto be used subsequently as the hydrogen carrier in the reactivationprocess. In such cases, complete separation of the solvent from thecatalyst is not necessary prior to effecting the reactivation.

One modification of a preferred procedure employing liquid phasecatalytic conversion, extraction of the partially spent catalyst with ahydroaromatic hydrocarbon, and liquid phase hydrogenation in thepresence of the same hydro-aromatic hydrocarbon is illustrateddiagrammatically in the accompanying drawing. As may be seen in thisdrawing, a suitable hydrocarbon fraction, such as a gas oil, is heatedin a conventional tube furnace I to a catalytic liquid phase crackingtemperature, and is introduced,

together with suspended powdered catalyst, into the top of a tower 2which serves as the cracking reactor.

The mixture of oil and catalyst flows downward through the reactor 2,and is withdrawn from the lower part of the tower, preferably at apointsomewhat above the bottom, as shown in the drawing. In this manner, asubstantial pro portion of the catalyst may settle to the bottom of thetower 2, where it can be withdrawn as a slurry and recycled to the topof the tower.

This recycling may suitably be effected in the manner shown in thedrawing, by injecting the hot charge oil into the catalyst slurryrecycle line 3. For this purpose the oil may be heated suficiently tocause partial vaporization at the pressure maintained in the crackingreactor 2.

7s The resulting vapors formed in the catalyst refrom condenser It.

cycle line 3 niay'then aid in' recycling the cata- 1 vaporizer l atsufliciently reduced pressure to effect flash vaporization of the bulkof the hydrov carbons. The vapors are then fractionated in aconventional manner to recover cracked naphtha and such other fractionsas may be desired.

Fractionating tower 5 and condenser 6 will serve for simplefractionation to recover naphtha and f-uel oil fractions;

The partially deactivated catalyst and a minor proportion of the highestboiling hydrocarbons of the crackedproduct settle to the bottom of theflash vaporizer '4 in the form of a slurry. This slurry is introducedinto an extraction tower I at an intermediate level, and the catalystsettles downward, countercurrent to an upflowing stream of a polycyclichydro-aromatic fraction. The

linear velocity of the rising hydrocarbon stream is maintainedsufliciently low to Prevent substantial amounts of catalyst fromreaching the top of the extraction tower l. The extract is removed fromthe top of the tower l and distilled in fractionator 8. A hydro-aromaticoverhead fraction from fractionator 8 is condensed in condenser 9 forrecycling to the extraction tower 1'.

Any catalyst removed from the extraction tower i may be recovered fromthe extract bottoms by filtration, or other suitable means. Since thetarry material constituting the extract bottoms has little value, it maybe burned to recover and simultaneously reactivate its catalyst content,if the amount of catalyst warrants this step. Generally the small amountof catalyst contained in the extract bottoms is not economicallyrecoverable, and is replaced by fresh catalyst. charged to the crackingreactor.

The extracted catalyst which settles to the bottom of the extractiontower l is withdrawn as a slurry of catalyst and hydro-aromatichydrocarbon. This slurry passes through a preheater Hi to one of anumber of alternately charged high pressure hydrogenation reactors H-Hprime. These reactors are maintained at a temperature of 750 F., and arepreferably equipped with suitable agitating means, not shown in thedrawing. Hydrogen or an inert gas is introduced into the reactor H at aninitial pressure of 1000-3000 lbs. per square inch, and the mixture isagitated for a period of 1-3 hours.

The slurry is then withdrawn from-the hydrogenation reactor ll andintroduced into a flash vaporizer l2 where the bulk of the hydrocarbonsare vaporized. The vapors may then be fractionated in fractionatingtower [3. An overhead fraction from tower l3 comprising low boilingaromatics resulting from the hydrogenation and. cleavage of polycyclicaromatics in the catalyst deposit and from hydrogenation and cleavage ofpolycyclic aromatics resulting from dehydrogenation of the polycyclichydro-aromatics employed as hydrogen carrier's is recovered as acondensate The fractionator bottoms comprise unreacted hydrocarbons ofthe polycyclic hydro-aromatic fraction employed as the hydrogen carrier,together with any hydrocarbons of the same boiling range produced in thehydrogenation reaction. This fraction may suitably be recycled to theextraction tower l, a shown in the drawing.

The reactivated catalyst and unvaporlzed hydrocarbons are withdrawn as aslurry from the bottom of the flash vaporizer II. The catalyst may berecovered from this slurry by filtration or other suitable means, ifdesired. However, 1 prefer to recycle the slurry directly to thecracking l5 reactor 2, as shown in the drawing.

My invention will be'iurther illustrated by the following specificexamples:

Example I A gas oil of about 38.5 A. P. I. gravity is cracked in theliquid phase at a temperature of about 700 F. and a pressure ofapproximately 500 lbs. per square inch, with a residence time of aboutone hour; employing approximately 20% of a powdered silica-aluminacracking catalyst, based on the weight of the oil charged. On aonce-through basis, a yield of about 30% cracked naphtha of 400 F.end-point is obtainable, with the carboncontent of the partiallydeactivated catalyst about 5% by weight of the catalyst, or 1% by weightof the charge. I

The partially spent. catalyst is charged to a high pressure reactor witha highly naphthenic distillate fraction of 350-500 F. boiling range, ina weight ratio of oil to catalyst of about 2/1. The mixture is agitatedand heated to a temperature of about 750 F'., at the vaporpressure ofthe hydrocarbons, for a period of 2 hours. The pressure is then releasedand the bulk of the hydrocarbons are flash vaporized from the catalyst,leaving a concentrated slurry for recycling. The carbon content of thecatalyst suspended in this slurry may be reduced to 0.8% by weight, orlower, on an oil-free basis; and the cracking activity of theregenerated catalyst should equal, and may exceed the activityobtainable by burning off the catalyst deposits.

Example II An alumina-molybdena hydroforming catalyst is employed infixed bed operation for hydroforming a heavy straight run naphtha ofabout 50 API gravity 250-400 F. boiling range, and a CFR octane numberof 44. Using a catalyst temperature of about 950 F., a pressure of 200lbs. per square inch, an oil feed rate of 1 volume of oil per volume ofcatalyst per hour, and a gas recycle rate of 2500 cubic feet per bbl. offeed, a

yield of 85-90% gasoline and 84 CFR octane num-' her is obtainable witha coke production of about 1% by weight of the charge. The process isoperated in 6 hour cycles, and the reactivation of the catalyst iseffected by reaction with tetralin at, a temperature of 750 using thhydroforming recycle gas to obtain an initial pressure of .2000 lbs. persquare inch. When employing two reactors alternately on stream, andusing all of the off-stream period for the reactivation reaction, lessonly the time required for charging and discharging, the coke depositson the catalyst may be substantially completely removed, and thecatalyst activity restored to a value as high, or higher, than can beobtained by burning oil the coke deposits.

It is to be understood,,of course, that the above examples aremerelyillustrative, and do not limit the scope of my invention. vCatalysts used in other types of hydrocarbon conversion processes may bereactivated in a similar manner, and other hydro-aromatic hydrocarbons,or other types of liquid phase hydrogen carriers may be substituted forthe particular materials employed in these sion processes may alsobe-operated at least par tially in the liquid phase in order to obtaincatalyst deposits of a nature particularly adapted for removal by myliquid phase hydrogenation process. In general, it may be said that theuse of any equivalents or modifications or procedure which wouldnaturally occur to those skilled in the art, is included in the scope ofmy invention. Only such limitations should be imposed on the scope of myinvention as are indicated in the appended claims.

I claim:

1. In a catalytic hydrocarbon conversion process in which the catalystbecomes at least partially deactivated by carbonaceous deposits and isreactivated and reused in the conversion operation, the steps whichcomprise subjecting deactivated catalyst to hydrogenation at a tempera-'ture in excess of 700 F. in the presence of a liquid phase hydrocarbonwhich is capable of substantial dehydrogenation under the catalystreactivation conditions, and separating the resulting liquid phase fromthe catalyst.

2. In a catalytic hydrocarbon conversion process in which the catalystbecomes at least partially deactivated by carbonaceous deposits and isreactivated and reused in the conversion operation, the steps whichcomprise subjecting deactivated catalyst to hydrogenation in thepresence of an at least partially saturated cyclic hydrocarbon at atemperature in excess of 706 F., and at a pressure sufilcient to providea liquid hydrocarbon phase, and separating the resulting hydrocarbonmixture from the catalyst.

3. In a cyclic catalytic hydrocarbon conversion process in which thecatalyst becomes at least partially deactivated by carbonaceous depositsand is reactivated and recycled to the conversion operation, the stepswhich comprise subjecting deactivated catalyst to the action of ahydroaromatic hydrocarbon at a temperature or 700- 900 F., and at apressure sufllcient to provide a liquid hydrocarbon phase, separatingthe resulting catalyst and hydrocarbon phases, and recycling thecatalyst to the catalytic hydrocarbon conversion process.

4. In a process for the catalytic cracking oi petroleum hydrocarbons inthe presenw of an aluminasilica catalyst in which the catalyst becomesat least partially deactivated by carbonaceous deposits and isreactivated and recycled to the cracking operation, the steps whichcomprise subjecting deactivated catalyst to the action of a hydrocarbonfraction comprising polycyclic hydro-aromatic hydrocarbons at atemperature of about 750 F., and at a pressure sufllcient to provide aliquid hydrocarbon phase, separating the resulting catalyst andhydrocarbon phases, and recycling the separated catalyst to the crackingoperation.

5. In a cyclic catalytic hydrocarbon conversion process, in which thecatalyst becomes at least partially deactivated by carbonaceous depositsand is reactivated and recycled to the conversion operation,- the stepswhich comprise eflecting the catalytic conversion in the presence of aliquid hydrocarbon phase, subjecting deactivated catalyst tohydrogenation at a temperature in excess of- 700 F,, and in the presenceof a liquid phase hydrocarbon which is capable of substantialdehydrogenation under the catalyst reactivation conditions. separatingthe resulting catalyst and hydrocarbon phases, and recycling theseparated catalyst to the hydrocarbon conversion operation.

6. In a cyclic catalytic hydrocarbon conversion process, in which thecatalyst becomes at least partially deactivated by carbonaceous depositsand is reactivated and recycled to the conversion operation, the stepswhich comprise eilecting the catalytic conversion in the presence of aliquid hydrocarbon phase, subjecting deactivated catalyst to solventextraction, subjecting the extracted catalyst to the action of an atleast partially saturated cyclic hydrocarbon at a temperature in excessof 700 F., and at a pressure suificient to provide a liquid hydrocarbonphase, separating the resulting catalyst and hydrocarbon phases, andrecycling the separated catalyst to the hydrocarbon conversionoperation.

7. In a cyclic catalytic process for cracking petroleum hydrocarbons, inwhich the catalyst becomes at least partially deactivated bycarbonacecus deposits and is reactivated and recycled to the crackingoperation, the steps which comprise effecting the cracking reaction inthe presence of a liquid hydrocarbon phase, subjecting deactivatedcatalyst to extraction by e. petroleum hydrocarbon fraction, subjectingthe extracted catalyst to the action of a hydro-aromatic hydrocarbon ata temperature of 700-900 F., and at a pressure sufficient to provide aliquid hydrocarbon phase, separating the resulting catalyst andhydrocarbon phases, and recycling the separated catalyst to the crackingoperation.

8. In a cyclic process for the cracking of petroleum hydrocarbons in thepresence of a silicaalumina catalyst, in which the catalyst becomes atleast partially deactivated by carbonaceous deposits and is reactivatedand recycled to the cracking operation, the steps which comprisesubjecting deactivated catalyst to extraction by a petroleum fractioncomprising polycyclic hydroaromatic hydrocarbons, subjecting theextracted catalyst to the action of said hydrocarbon fraction at atemperature of about 750 F., and at a pressure suflicient to provide aliquid hydrocarbon phase, separating the resulting catalyst andhydrocarbon phases, and recyclin the separated catalyst to the crackingoperation.

MEREDITH M. STEWART.

I CERTIFICATE OF'CORRECTIONO Patent No, 2 567pb-7b-o Tamary 16, 19 -5.1

MEHEDIE H. STEWART It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: Page 5, sec- 0nd column lines 1;; and n Example II, for WMread --CFR.R--; and that the said Letters Patent should be read withthis correction therein that the same may conform to :hhe record of thecase in the Patent Officeo Signed and sealed thisjth day of June, A. D.19150 Leslie Frazer (Seal) Acting Commissioner of Patents,

